
2 Aggregate uses
Underlying load bearing material for foundations and pavements
Ingredients in portland cement and ashpalt concrete

Fine agg (sand) dimensions
Less than 4.75 mm

Coarse agg (stone or gravel ) dimensions
greater than 4.75 up to 9.5 and 37.5

Concrete Agg minerals (2)
Mafic and Felsic

Mafic properties
 Minerals rich in Fe and Mg
 Dark green, brown, black

Felsic
 Minerals rich in silicon, aluminium, sodium and potassium
 Light coloured, i.e grey, white

Coarse aggregate rocks (3)
 Igneous
 Sedimentary
 Metamorphic

Igneous examples and formation
 Basalt and Granite
 formed by cooling and solidifying of magma and lava

Sedimentary examples and formation
 Greywacke and Limestone
 Products of erosion, accumulates as sediment then buried, compacted and cemented. Occurs under pressure

Metamorphic examples and formation
 Marble and Schist
 formed within earth's crust  transformation of rocks via heat.

Auckland and Dunedin use what rocks
Basalt and Phenolite

Tauranga and Taranaki use what rocks
Andesites

Nelson and Invercargill use what rocks
Mixed gravels

Other types of of aggregate
Crushed air cooled blast furnace slag
Natural and manufactured light weight aggregate
Recycled concrete aggregate

Aggregate Processing (4)
 1. Crushing
 2. Screening  separates material into sand etc.
 3. Washing  removes salt, clay or dust. (affects bonding)
 4. Transportation

Evaluation of aggregate sources (4)
Aggregates selected to meet project requirements
Continual sample and test materials
Physical and chemical properties

What does the use of aggregate add to underlying material of base course? (2)
1. Adds stability  function of inter particle friction between aggregate clay, or silt binder in voids
2. Provides drainage layer  clay and silt may block drainage paths

Aggregate use in Portland Cement Concrete (4)
 1. 6075% of volume
 2. Acts as filler to reduce amount of cement paste
 3. Greater volume stability than cement paste
 4. Need to maximize volume of agg for economy and quality

Aggregate use in asphalt concrete
 1. 80% of volume
 2. Asphalt acts as binder to hold aggregate together, not enough strength to lock particles into position.
 3. Strength and stability depend on interparticle friction

Important properties of Aggregate (10)
 1. Specific gravity (bulk density)  relates to packing density
 2. Porosity voids
 3. Absorption  ability and amount of absorbed water
 4. Moisture content
 5. Shrinkage  due to drying
 6. Gradation and fitness modulus size distribution
 7. Chemical re activity  durability
 8. Particle shape  interlock and water deman
 9. Modulus of elasticity
 10. Compressive strength

Aggregate Absorption =
moisture content @SSD / mass dry aggregate (%)

Abs for coarse aggregate
0.24%




Specific Gravity
ratio of the mass unit volume of the material to weight of the same volume of water at 23 degrees

Specific gravity Ga =
Mass of aggregate/ mass of equal volume of water

Unit weight (density ) of aggregate (2 equations)
Unit weight = Mass of aggregate / volume of aggregate
Unit weight = specific gravity Ga times by density of water

Types of specific gravity (3)
Bulk Specific gravity  volume of pores included
Apparent Specific gravity  volume of pore excluded
Effective specific gravity

A B and C equals....
S equals..
 A= Dry Mass
 B = SSD mass OR mass of pycnometer filled with water (sand)
 C = submerged mass
S = Mass of sand , SSD

Bulk specific gravity @SSD (Ga)
Ga = B/(BC)

Unit weight of SSD
B/(BC) times density of water

Bulk Specific Gravity (DRY)
Gdry = A/ (BC)

Unit weight (DRY)
A/ (BC) times density of water

Apparent Specific Gravity of aggregate
A/ (AC)

Apparent unit weight
A/(AC) time density of water

Apparent unit weight (density ) of aggregate
Mass of aggregate/ volume not accessible to water

Effective Specific Gravity equation (Gse)
What is effective volume
Gse = dry mass of aggregate (A)/ effective volume
Effect volume = vol of agg particle + vol of water perm pores not filled with bitumen

Absorption
SA/A times 100

Specific gravity in SSD for SAND
Unit weight?
Gssd = S/(B+SC)
unit weight = above times density of water

Dry specific gravity of SAND
G dry = A/ (B +S C)

Bulk density equation
what does it depend on?
Mass of dry aggregate / volume of container
Density depends on S.G of agg, particle shape and surface texture.

Bulk unit weight of normal agg compared to unit weight
Bulk unit weight 1200 to 1700 kg/m^3
Unit Weight = 2400 to 2900 kg/m^3

Typical compressive and tensile strengths
 CS  65270 MPa
 TS  2 to 15 MPa

Modulus of elasticity of aggregates affects... in concrete
ranges
 Magnitude of shrinkage and creep in concrete
 9.9 to 69 GPa

Free surface moisture content
and correction equation
SM = MwetMssd/Mssd time 100
W correction = Mssd times (MCabs)/ (1+ abs)

Total Moisture equation (SSD)
MwetMdry/ Mdry times 1000

